1. Field of the Invention
An aspect of the present invention relates to a substrate processing apparatus to process a plurality of substrates, and more particularly, to a heating unit that heats a processing chamber in which a plurality of substrates are processed, and a substrate processing apparatus having the same in which the heating unit is cooled in a short time to thereby reduce a time required to cool the processing chamber.
2. Description of the Related Art
Flat panel display devices have replaced cathode ray tube display devices due to characteristics such as light weight, thin thickness, and so on. Typical examples thereof include liquid crystal display devices (LCDs) and organic light emitting diode (OLED) display devices. In comparison with LCDs, OLED display devices are excellent in brightness and viewing angle characteristics and require no backlight, so that they can be ultra thin display devices.
OLED display devices use a phenomenon in which electrons injected from a negative electrode (cathode) and holes injected from a positive electrode (anode) are recombined to create excitons in an organic thin film such that light having a specific wavelength is emitted by the release of energy resulting from de-excitation of the excitons. The OLED display devices are classified into two types, a passive matrix type and an active matrix type, according to the driving method. Active matrix type OLED display devices include a circuit using a thin film transistor (TFT).
These flat panel display devices are manufactured by forming a thin film having electrical properties on a substrate in a predetermined pattern using an organic or inorganic compound, and then heat-treating the formed thin film. The process of forming the thin film is generally divided into physical vapor deposition (PVD) processes such as a sputtering process of applying plasma to a target and depositing a thin film on a substrate, and chemical vapor deposition (CVD) processes such as an atomic layer deposition (ALD) process of spraying a reaction gas containing a source material on a substrate and forming an atomic layer of the source material on the substrate through a chemical reaction.
The CVD processes have higher uniformity and step coverage of the thin film, and allow a plurality of substrates to be processed at one time, compared to the PVD processes, and thus are widely used in processes of forming an amorphous silicon layer and an insulating layer such as a nitride layer or an oxide layer.
Typically, to simultaneously form a thin film on a plurality of substrates using a CVD process or perform heat treatment on the thin films, a substrate processing apparatus includes a boat on which the substrates are stacked, a processing chamber providing a space in which the substrates can be processed, a transfer unit carrying the boat into or out of the processing chamber, and a heating unit located outside the processing chamber. The transfer unit may include a heat insulating section such that the processing chamber can be readily heated therein by the heating unit.
This substrate processing apparatus is designed to directly introduce external air into the processing chamber or allow the external air to flow between the processing chamber and the heating unit, after the substrates stacked on the boat are completely processed. In the case where the external air is directly introduced into the processing chamber, it is possible to cool the processing chamber in a short time, but there is a possibility of impurities being deposited on the substrates stacked on the boat. Further, in the case where the external air flows between the processing chamber and the heating unit, a time required to cool the processing chamber is increased due to heat of the heating unit, and thus an overall processing time is increased.